a. What is the pH of a solution containing 0.100 mol dm^–3 ethanoic acid and 0.100 mol dm^–3 sodium ethanoate? (Ka of CH₃COOH = 1.74 × 10^–5 mol dm^–3)

b. How many moles of sodium ethanoate must be added to 2.00 dm³ of 0.0100 mol dm^–3 ethanoic acid to produce a buffer solution of pH 5.40?

c. Explain why the pH of a solution containing 0.100 mol dm^–3 ethanoic acid and  0.100 moldm^-3 sodium ethanoate does not change significantly when a small amount of hydrochloric acid is added.